Inheritance and strain distribution of a persistent hyaloid vascular system in mice

The mode of inheritance of a persistent hyaloid vascular system was investigated in an inbred strain of Senescence-Accelerated Mouse P9 (SAMP9) by conducting crosses between SAMP9 and SAMR1, a strain which shows normal regression of the hyaloid vascular system. We also examined the distribution of this abnormality in 12 inbred SAM strains and in eight commonly used inbred strains of mice. Ophthalmoscopic examination of the eyes of 5-week-old mice, which have transparent lenses, revealed the persistence of a hyaloid vascular system in only one female F1 hybrid out of 66 offspring. The observed segregation ratio of affected to unaffected mice was 25:52 in males and 37:44 in females, following the reciprocal backcross progeny between SAMP9 mice and F1 hybrids. The results of the strain distribution study indicated that 8-97% of the mice among six strains of SAM exhibited the persistence of a hyaloid vascular system, whereas the other inbred strains did not exhibit this abnormality. These observations suggest that at least two major genes may contribute to the persistence of a hyaloid vascular system, and suggest that the SAM strains comprise a group of related inbred strains.